1. Field
The disclosure relates to analog switches for radio-frequency (RF) circuits.
2. Background
State-of-the-art wireless devices are commonly designed to support radio processing for multiple frequency bands and operating modes. For example, a single smart phone may be required to connect to a wide-area network (WAN), a wireless local-area network (WLAN), and/or other radio-frequency (RF) communication links such as Bluetooth, etc. To accommodate this feature, multiple switches (e.g., series and/or shunt switches) are commonly provided to share one or more antennas amongst circuitry for each of the bands and modes.
In certain scenarios, the existence of large-amplitude voltages (e.g., due to high-power voltages generated by a transmit or TX signal path) across such multiple switches may undesirably lead to non-linear distortion, which can interfere with accurate transmission and reception of desired signals by the device. Prior art techniques for improving switch linearity include setting both the gate and substrate bias voltages of switch transistors to be substantially more negative than the expected large-amplitude voltages, when it is desired to turn the corresponding switches off. Ideally, no current should flow through the switches as a result of such negative bias voltages being provided. In practice, however, undesirable leakage current may nevertheless flow, e.g., through the transistor substrates.
It would thus be desirable to provide effective techniques for improving the linearity of multiple switches that do not suffer from the drawbacks of the prior art.